May 23, 2014
Fruit Flies Take Time To Think Before Making Difficult Decisions
Lawrence LeBlond for redOrbit.com - Your Universe Online
It is common knowledge that most humans think before they act. A new study, published in the journal Science, makes the case that this cognitive ability can also be found in the fruit fly, and it seems these tiny insects take longer to make more difficult decisions, just like humans do.
In the study, researchers from the University of Oxford's Centre for Circuits and Behaviour asked fruit flies to distinguish between ever closer concentrations of a particular odor; they found that the flies do not just act instinctively or impulsively, but rather seemingly accumulate information before making a choice.
"This is the clearest evidence yet of a cognitive process running in a very simple brain," Prof Gero Miesenböck told BBC News. "People tended to think of insects as tiny robots that just respond reflexively to signals from the environment. Now we know that's not true."
Gathering information before making decisions has been considered a sign of higher intelligence, mostly known in primates and humans. “What our findings show is that fruit flies have a surprising mental capacity that has previously been unrecognized.”
Scientists have long been fascinated by decision-making, noted Prof. Miesenböck.
“Going back to the 19th century, psychologists have measured how long it takes humans to make up their minds,” he told New York Times. “Usually if you give people a hard perceptual choice, they take longer, because the brain needs to integrate information until it has enough to make a decision.
“This is the first time in an animal as low as a fruit fly we have been able to show that similar processes occur… We were surprised,” Prof Miesenböck said.
In the research, the team also showed that the gene FoxP, active in a small set of neurons within the brain, is involved in the fruit fly’s decision-making process.
The researchers gave fruit flies choices of two odor concentrations. The odors were presented to the flies at the opposite ends of a narrow chamber. They observed the flies make a single choice after having trained them to avoid one concentration. When the concentrations were very different and easy to tell apart, the flies made quick decisions and almost always moved toward the correct odor. When the odors were very close and difficult to distinguish, the flies took longer to make a decision, and often made more mistakes in the process.
This is a pattern that psychologists have studied for decades in humans.
"The same mathematical models that describe human decision-making also capture the flies' behaviour perfectly," Prof Miesenböck told the BBC’s Jonathan Webb. "That's remarkable."
This suggests that the fly’s brain is gradually accumulating evidence until it has enough information to make a relatively confident choice.
The team traced the effect of FoxP to about 200 neurons, or about 0.1 percent of the fruit fly’s total brain-cell count (200,000), and all within the “mushroom bodies” – a pair of brain compartments already known to be important for learning. When making other disruptive changes to these same 200 neurons, the team was able to produce a similar effect.
The team discovered that fruit flies with mutations in the FoxP gene took longer than normal flies to make decisions when the odors were difficult to distinguish, becoming indecisive. This implicates these neurons in the evidence-accumulation process the flies use before committing to a decision.
“Before a decision is made, brain circuits collect information like a bucket collects water. Once the accumulated information has risen to a certain level, the decision is triggered. When FoxP is defective, either the flow of information into the bucket is reduced to a trickle, or the bucket has sprung a leak,” lead author Dr Shamik DasGupta, explained in a statement.
Fruit flies have only one FoxP gene, while humans have four. Human FoxP1 and FoxP2 have been previously associated with language and cognitive development. These genes have also been linked to the ability to learn fine movement sequences, such as playing a piano, explained the researchers.
“We don't know why this gene pops up in such diverse mental processes as language, decision-making and motor learning,” says Prof Miesenböck. However, he speculates: “One feature common to all of these processes is that they unfold over time. FoxP may be important for wiring the capacity to produce and process temporal sequences in the brain.”
“FoxP is not a "language gene", a "decision-making gene", even a "temporal-processing" or "intelligence gene". Any such description would in all likelihood be wrong. What FoxP does give us is a tool to understand the brain circuits involved in these processes. It has already led us to a site in the brain that is important in decision-making,” added Prof Miesenböck.
Prof Matthew Cobb of the University of Manchester, who was not involved in the study, said the experiments are impressive, adding that it is of no surprise that it took five years to complete this study.
"The data are incredibly solid," he told the BBC.
Prof Simon Fisher, of the Max Planck Institute for Psycholinguistics, is one researcher who was involved in the discovery of FoxP2 in humans. He told Jonathan Webb at BBC News that the latest findings were exciting and contribute to a "fascinating picture" of the gene and its history.
He explained that work like this in other species suggested the role of FoxP2 in humans is “built on ancient functions,” relating to the wiring of neural circuits and how they change as we learn.
"It turns out that this is a gene that has been around for a really long time in evolutionary history, doing interesting things in the brain," he said.